This invention relates to injection control valves for fuel injection systems in internal combustion engines and, more particularly, to new and improved injection control valves which provide more effective operation of a fuel injection system.
In German Offenlegungsschrift No. 35 11 492, an injection control valve for a fuel injection system has an electromagnetic or piezoelectric actuating device arranged to move a valve-closing member axially into a position in which it opens a connection between a compression chamber and another chamber when actuated, and a compression spring moves the valve-closing member to close the connection when the device is deactivated. To minimize the force required for the actuating device to move the valve-closing member into the position opening the connection and the spring force required to move the valve-closing member into its closed position, the valve-closing member and its valve seat are designed so that the valve-closing member has no surface exposed to the fuel pressure in the opening and closing direction when the connection is closed. Immediately after the valve-closing member is separated from its seat, however, it exposes those surfaces so that the force applied by the actuating device is supplemented by the fuel pressure in the compression chamber which is in communication with a working chamber of the fuel pump.
Such injection control valves provide the advantage that the fuel injection process can be completed even before the end of the working stroke of the fuel pump piston by reducing the fuel pressure in the compression chamber which is in communication with the fuel injection valve of the internal combustion engine. Further closing of the valve, i.e., movement of its valve-closing member into the position closing the connection between the compression chamber and the other chamber, is effected by the associated compression spring upon deactivation of the actuating device after the end of the working stroke of the pump piston, i.e., after the end of the delivery stroke of the pump.